Fair Value Measurements (Details) - Fair value measurements on recurring basis - Total - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Assets:
Total fair value	$ 224,094	$ 207,963
Defined Benefit Pension Plans
Assets:
Total fair value	224,094	207,963
NAV
Assets:
Total fair value	224,094	207,963
NAV \| Defined Benefit Pension Plans
Assets:
Total fair value	$ 224,094	$ 207,963

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant